1. Field of the Invention
This invention relates generally to threaded receptacles, and more particularly to a threaded electrical socket for a light bulb and a method of making the socket which includes non-binding threads and electrical contacts which readily can be connected to the socket without any additional fasteners and maintain continuity between the electrical contacts and the light bulb during vibration or extreme tolerance conditions between the light bulb threads and the socket threads to eliminate intermittent contact therebetween.
2. Description of the Related Art
Light bulb sockets or fixtures typically are cylindrical in shape, closed at one end, open at an opposite end and threaded on their interior wall surfaces to accept the threads of the light bulb. Two electrical contacts are secured in the inside of such sockets so that one contact engages with the base or bottom of the light bulb inserted in the socket and the other contact engages the side wall of the base of the light bulb. The electrical contacts typically are connected to the socket by fasteners, such as screws, and the sockets usually are made in more than one piece to enable easy molding of the sockets and assist in assembling the contacts within the socket.
These existing light bulb sockets typically are made from a non-conductive material, such as plastic, and can be utilized in a variety of lighting situations including appliances such as refrigerators, stoves and similar articles. An example of such a socket is shown in U.S. Pat. No. 3,783,435 which is assigned to the assignee of the present application.
That patent discloses a molded plastic light bulb accommodating housing formed of two symmetrical halves having electrical terminal members projecting therethrough, one for contacting the light bulb base and the other for contacting the base periphery. The electrical terminals are placed in position within one of the two symmetrical halves which then are welded together. The exterior surface of the housing includes engagement members for mounting the socket to a panel, such as a panel which forms the inner lining for a refrigerator. The socket is designed so that when mounted in an aperture of a panel, the axis of the socket will be positioned at a predetermined angle with respect to the plane of the panel.
Due to the large number of parts, these light bulb sockets and contacts are difficult to assemble, especially when small contacts and corresponding fasteners or fastening methods are utilized. Additionally, it is difficult to position such contacts within the socket to maintain continuity between the electrical contacts and the light bulb.
These assembly and positioning problems are even more pronounced when a socket is molded in one-piece. Typically, to mold a one-piece socket, the mold core and corresponding machinery used to form the interior of the socket and the interior threads are of a complex, expensive design which usually include either a collapsible mold core or a mold core which is unscrewed from the socket as it is removed after molding. These complex mold cores are necessary to provide interior screw threads that substantially match a desired thread standard corresponding to the threads on the light bulb.
An easier and less expensive way to form a one-piece socket is with a simple non-collapsible mold core having exterior threads which form the desired threads on the socket interior. Such a mold core merely is pulled out or stripped from the socket after molding. As the mold core is pulled out, however, the crests of the threads on the interior of the socket become deformed as the crests on the threads of the mold core are passed thereover. Typically, this deformation leaves the interior socket threads with a thread profile that is outside the thread profile of the desired thread standard. As a result, when a light bulb or thread testing gauge later is threadingly inserted into the socket, the threads do not properly match and binding occurs between the socket and bulb or gauge threads.
It therefore is desirable to provide an electrical socket having threads and electrical contacts which readily can be connected to the socket without any additional fasteners and which maintain continuity between the contacts and the light bulb, especially during vibration or extreme tolerance conditions between the socket threads and the bulb threads, to eliminate intermittent contact therebetween.
It also would be desirable to provide a one-piece molded socket formed with a simple mold core which merely can be pulled out of the socket after molding and provides the socket threads with a thread profile which closely matches the desired standard for proper threaded bulb engagement while eliminating any thread binding.